Television receiver



DecQSl, 1940. K. SCHLESINGER TELEVISION RECEIVER Filed Sept. 6, 1935AIAAAA I VVVVV Patented Dec. 31, 1940 TELEVISION RECEIVER KurtSchlesinger, Berlin, Germany, assignor, b mesne assignments, to LoeweRadio, Inc., acore r poration of New York Application September 6, 1935,SerialNo. 39,467, t

In Germany September 8, 1934 1 1 Claim.

The invention rel'atestothesupply of anode D. C- potentials to completetelevision receivers which comprise a radio receiver in combination witha cathode-ray television tube andan appertaining relaxation oscillationgenerator. Ina receiving system of thiskind there has usually beenperformed heretofore in practice a distribution of thecurrent supplyover two transformers, of

l whichthe one Supplies all heating alternating currents for thecathodes, whichmay be at earth potential or approximately atearthpotential, whilst theothenin conjunction with rectifiers, produces"all the anode potentials. The disadvantages of a distribution of thiskind on the anode side .consistsjin the fact that the three circuits,receiver, screen apparatus and television tube, necessarily influenceeach other. In particular it has not been possible to increase the anodepotential employed for. the television tube independently of theotherpotentials and at the same time keep the picture size constant withincreasing light intensitywithout simultaneously increasing thepotential of the receiver. Anadditional disadvantage associated withall-high-tension systems consists in the frequent break down of. thesmoothing condensers in practice. If the anode of the television tubeand the deflecting plate are earthed, so that the cathode is negativeto, theextent of several thousand volts in relation toearth, a breakdown of this kind is in practice nearly always associated with loss ofthe television tube, asupon the breakdown the potential of the cathodepath israised instantaneously to 1 anode potential, whereby highemissions of a destructive kind are able to take place. ,Th eaccompanyingdrawing shows a mainsconnection diagram, which is free fromall of these disadvantages. It is based on a system for potentialdoubling similar to the well known Greinacher connection which, however,has been particularly modified for' television purposes. Thehigh-tension transformer is derived from. two separate transformerwindings I, 2 and 3, each having a separate iron core, of which thewindings I and 2 supplies solely the anode potential for the relaxationoscillation generator and for the television tube, whilst the winding 3assumes merely the feeding of the receiver with anode direct current. Itis accordingly possible to vary the excitation of the primary Winding 4,which belongs to the secondary winding l/?, in itself, for example bymeans of a series resistance 5, without any effect on the potential ofthe receiver. With a variation of this kind at 4 the anode potential andrelaxation potential arcincreased toan equal amount, so'that the size-ofthe image remains exactly constant, whilst the intensity ,of the imageincreases with the anode potential of the television tube. The supplysection I, 2, 4 operates in accord: ance with the invention in half-waveconnection, whilst the anode potential section 3 operates in full-Wave"connection; This is possible because the requirement for anodepotential on thepart' of the screen apparatus and thQ'BI'HiLlI]. tube iscomparatively smalljg Thus, for example, in a Braun tube of present-dayconstruction with a relaxation apparatus supplying relaxation volt.-ages of reversed phase and 2000 volt electrodes an anode potential of,700 volts is sufficient for the relaxation oscillation generator.This'is already obtained at theterminal 6 when the winding 2 in effecthas merely '500volts'. The condensers I and. 8 are accordingly'alsoconstructed merely with a testing potentialof approximately 1,500 volts.As in the case of the terminal 6 the double potential would developentirely alone at the terminal 9. Since this is not quite sufficientthere is, conveniently employed an auxiliary winding I of 300 volts ineffect. There then results at the terminal 9 a potential amountingasfollow:

The condensers Ill.v and II, therefore, .merely require to withstand thediiference in potential between 9 and 6, and to not break down.

According to a subsidiary feature of the invention a variable impedance32 ispr'ovided in the lead connection to the relaxationoscillationgenerator apparatus 2|, said. impedance being arrangedbetween the two condensor groups 1, I0. and 8, I I. By varying thisimpedance preferably of the form of an ohmic resistance an independentregulation of the proportion of the image brightness on the one hand andof the size of the image on the other hand may be performed. In thiscase an adjustment of the anode-potentials for the relaxation generatorsmay be performed without variation of the anode potentials for the Brauntube.

According to the invention, the Braun tube I2 is connected with anearthed cathode I3 earthed through a condenser 30, and its anode I4 israised to a positive high tension against earth. The deflecting platesI5 and I6 are preferably connected within the tube with the anode bymeans of fixed resistances I! and I8. The transmission condensers I9 and20, which are necessary for feeding the relaxation oscillations on thepart of the screen apparatus 2| may be accommodated with advantage inthe high vacuum of the television tube l2 in order to render impossiblea breakdown of these condensers operating with a working potential ofalmost 2000 volts. The time circuits l9/l'l and 18/20 should be selectedwith consideration to the relaxation frequencies to be transmittedthereto. The condensers, become small and handy the larger the leakageresistances l1 and I8 are capable of being made, and these, particularlyin the case of a negative bias between plates and anode and location ina vacuum, may amount to 1 megohm. In this case the transmission ofrelaxation oscillations with 25 image changes is already quitesuccessful with a capacity of 0.05 M. F. v

In the connection system according to the invention not only arefluctuations in the potential of the television anode counterbalanced byfluctuations of equal size and equal direction in the anode potential ofthe scanning apparatus, but also the humming potentials of both circuits6 and 9 compensate each other there belong also co-phasal low anodepotentials of 21, so that the form of image is always confined bystraight lines. Owing to this natural compensation the smoothingrequired (22/ l I) may be kept so low that the loss of potential at thecondenser l I as compared with ID remains less than 2%. Also in thisthere is to be recognized an appreciable improvement as compared withthe Braun tube connection systems with earthed anode of 12, in which theripple elimination of the control circuit l3 requires to be made betterthan 10- The provision of a metallic deposit on the outer wall 23 of thetube and the connection thereof with earth is not to be avoided owing tothe effect exerted by the surroundings. a

In the drawing there is also shown the connection of the grid cathodecircuit of l2 with the final tube of the receiver, the rectifier 24.According to theinvention there is selected also v in this case a bridgeconnection for steadying the grid circuit andfor adjusting the correctmean value of the light'intensity. This consists of the final tube 24with its anode resistance 25 on the one hand and the potentiometer 26 onthe other hand. The latter may be operated from the exterior, or mayalso be mechanically coupled with the switch for switching on or ofi thereceiver. Even with traces of ripple at the smoothing capacity 21 nohumming stripes occur in the image, because the grid bias of thetelevision tube is situated in the bridge diagonal to 21, and the ripplepotential in the anode feed for the receiver is accordingly eliminatedin the control circuit for the intensity.

In view of the very considerable consumption of current in the case of aradio receiver for television purposes having a large number of stages,amounting to approximately -100 milliamperes, two-way rectification 3 3is, in accordance with the invention, retained in this part of therectifier for the purpose of effecting economy in smoothing means. Theheating of the television tube I3 is derived from a 4-volt winding 28,which is preferably also wound on to the common heating transformer 29,supplying the heating filaments of all tubes operating in the receiver.An interfering hum in the winding supplying the heating voltage for thetelevision tube is prevented by a capacity 30. For the same purposethere may be provided in addition an earthed protective coil 3| andearthing of the iron core 29.

I claim:

In a television receiving apparatus wherein is included a cathode raytube provided with at least a cathode andan anode and a controlelectrode and wherein is also included electron beam deflecting meansfor deflecting the developed cathode ray and a relaxation generatorconnected to energize the beam deflecting means, a power supply systemincluding a pair of input terminals adapted to be energized from asource of alternating current voltage, a transformer having a primaryand a secondary winding, a connection from the primary winding to theinput terminals to supply energy to the primary winding and to causeenergization of the secondary winding, a pair of half-wave rectifiertubes, a connection from the end terminal of the secondary winding tothe anode and cathode elements of one of the rectiflers, a connectionfrom an intermediate point on the transformer secondary winding and oneend terminal of the said winding to the anode and cathode of the otherrectifier with the said other rectifier being connected in oppositepolarity to the first rectifier, a filter comprising series resistanceand parallel capacity connected to the output circuit of each rectifier,and a plurality of output terminals for the system whereby between oneof said output terminals and a predetermined point of constant potentiala voltage is developed to energize the relaxation generator and betweenthe second terminal and the said point of fixed potential is developed avoltage which is a multiple of that appearing at the first terminal soasto energize the anode cathode elements of the cathode ray tube andwhereby voltage fluctuations tending to alter the velocity of thecathode ray beam by variations in anode voltage are compensated in apattern traced thereby by proportional variations controlling therelaxation generator to develop the energy to deflect the cathode raybeam.

' KURT SCHLESINGER.

